CVE-2021-40824

low-risk
Published 2021-09-13

A logic error in the room key sharing functionality of Element Android before 1.2.2 and matrix-android-sdk2 (aka Matrix SDK for Android) before 1.2.2 allows a malicious Matrix homeserver present in an encrypted room to steal room encryption keys (via crafted Matrix protocol messages) that were originally sent by affected Matrix clients participating in that room. This allows the attacker to decrypt end-to-end encrypted messages sent by affected clients.

Do I need to act?

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0.24% chance of exploitation
EPSS score — low exploit probability
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Not on CISA KEV list
No confirmed active exploitation reported to CISA
?
Patch status unknown
Check vendor advisories for fix availability and mitigation guidance
5
CVSS 5.9/10 Medium
NETWORK / HIGH complexity

Affected Products (2)

Element
Matrix-Android-Sdk2

Affected Vendors

Matrix

References (4)

Patch https://github.com/matrix-org/matrix-android-sdk2/releases/tag/v1.2.2
Vendor Advisory https://matrix.org/blog/2021/09/13/vulnerability-disclosure-key-sharing
Patch https://github.com/matrix-org/matrix-android-sdk2/releases/tag/v1.2.2
Vendor Advisory https://matrix.org/blog/2021/09/13/vulnerability-disclosure-key-sharing
26
/ 100
low-risk
Severity 18/34 · Moderate
Exploitability 1/34 · Minimal
Exposure 7/34 · Low